1. Field of the Invention
The present invention relates to image processing apparatus and method thereof to perform plural types of image processings using plural processors on supplied data.
2. Description of the Related Art
An image processing apparatus such as a printer which inputs PDL data in which data is described in Page Description Language (PDL) and generates a raster image based on the PDL data is known. This image processing apparatus conducts two procedures of interpretation of input PDL data and rendering processing. As representative algorithm in this rendering processing, painter's algorithm, scan-line algorithm and the like are known. In the conventional image processing apparatus, the rendering processing is performed with hardware or software using such algorithm. In recent years, an idea of realizing the rendering processing in an image processing apparatus with a software device having plural processors is proposed.
When a raster image is generated by rendering-processing PDL data, processings of edge detection, overlap determination, coloring and the like with respect to a PDL-described object are required. Accordingly, this apparatus has an edge detection PDL command processing section to track edges of a PDL-described image and a level determination PDL command processing section to determine an overlap portion between objects outputted from the edge detection PDL command processing section and determine a visible object. Further, the apparatus has a color creation PDL command processing section to receive a start signal from the level determination PDL command processing section and start color creation and an image data PDL command processing section to process image data, and further, realizes PDL processing by a color composition PDL command processing section.
When the PDL processing is performed with plural processors, the process load on a processor to perform the edge detection PDL command processing may be heavy while that on a processing to perform the color composition PDL command processing may be light in accordance with content of PDL data. In this manner, the process load differs among the processors to perform the respective processings.
The difference in the process load on the processors to perform the respective processings is not limited to the PDL processing, but it generally occurs in a series of image processings for conversion of print data into a raster image using plural processors. Thus, an image processing apparatus in which load balancing in image processing is realized among plural processors is proposed.
Japanese Patent Laid-Open No. 2000-353152 (document 1) discloses a graphic processor having a pipeline structure, in which plural processors are serially connected, and a predetermined processor performs a geometrical operation. The load of a predetermined processor is determined, and if it is determined that the load of the processor is highly loaded, a processor which does not perform the geometrical operation under normal conditions performs a part of the geometrical operation performed by the predetermined processor.
Further, Japanese Patent Laid-Open No. 2006-133839 (document 2) discloses an image processing apparatus which sequentially performs plural types of image processings with plural processors. Each processor has a dedicated instruction operation section in addition to a general instruction operation section. Upon normal processing, a first program described in general instructions and dedicated instructions is executed. Upon auxiliary processing determined based on load balance, a second program described in general instructions is executed.
However, in these documents 1 and 2, one of the plural processors periodically monitors and estimates the load on all the processors and executes a task to correct the load balance. In addition, in a case that the total number of processors is increased for improvement in performance of the entire system, the process load of the task for load balancing is also increased. That is, in a case that the load monitoring and the task to correct the load balance are added to the image processing apparatus, the throughput of the entire system in the image processing apparatus having plural processors is degraded.